Development of pulsed processes for the manufacture of solar cells. Final report

Abstract

The results of a one and half year program to develop the processes required for low-energy ion implantation for the automated production of silicon solar cells are described. The program included (1) demonstrating state-of-the-art ion implantation equipment and designing an automated ion implanter, (2) making efforts to improve the performance of ion-implanted solar cells to 16.5 percent AM1, (3) developing a model of the pulse annealing process used in solar cell production, and (4) preparing an economic analysis of the process costs of ion implantation and furnace annealing. During the program, phosphorus ions at an energy of 10 keV and dose of 2 x 10/sup 15/ cm/sup -2/ were implanted in silicon solar cells to produce junctions, while boron ions at 25 keV and 5 x 10/sup 15/ cm/sup -2/ were implanted in the cells to produce effective back surface fields. An ion implantation facility with a beam current up to 4 mA and a production throughput of 300 wafers per hour was designed and installed. A design was prepared for a 100-mA, automated implanter with a production capacity of 100 MW/sub e/ per year. Two process sequences were developed which employ ion implantation and furnace or pulse annealing. The JPL-Solar Array Manufacturing Industry Simulation (SAMIS) computer program was used to determine costs for junction formation by ion implantation and various furnace annealing cycles to demonstrate cost effectiveness of these methods.